PDC drill bit using optimized side rake angle

Abstract

A fixed cutter drill bit and a method for designing a fixed cutter drill bit includes simulating the fixed cutter drill bit drilling in an earth formation. A performance characteristic of the simulated fixed cutter drill bit is determined. A side rake angle distribution of the cutters is adjusted at least along a cone region of a blade of the fixed cutter drill bit to change the performance characteristic of the fixed cutter drill bit.

1. A method for designing a fixed cutter drill bit, comprising:
 simulating the fixed cutter drill bit drilling in an earth formation, wherein the fixed cutter drill bit comprises cutters in a cone region and a nose region having side rake angle; 
 determining at least one performance characteristic for the fixed cutter drill bit; 
 adjusting a side rake angle of at least one cutter of the fixed cutter drill bit, wherein the adjusting involves adjusting a cutter along at least one of the cone region and the nose region of the fixed cutter drill bit; and 
 repeating the simulating, the determining, and the adjusting until the at least one performance characteristic meets a selected criterion. 
 
     
     
       2. The method of  claim 1 , wherein the adjusting involves a cutter along the cone region of the fixed cutter drill bit. 
     
     
       3. The method of  claim 1 , wherein the adjusting involves a cutter along the nose region of the drill bit. 
     
     
       4. The method of  claim 1 , wherein the adjusting produces a side rake angle distribution such that cutters positioned in the cone region toward a center of the drill bit have larger side rake angles than cutters positioned in the nose region of the drill bit. 
     
     
       5. The method of  claim 4 , wherein the side rake angle distribution is adjusted such that cutters in the cone region have progressively smaller side rake angles from the center outward toward the nose region. 
     
     
       6. The method of  claim 1 , wherein the adjusting produces a side rake angle distribution such that a cutter in the cone region has a side rake angle no greater than about 15 degrees and a cutter in the nose region has a side rake angle smaller than the side rake angle of the cutter in the cone region. 
     
     
       7. The method of  claim 1  wherein determining at least one performance characteristic for the simulated fixed cutter drill bit comprises determining at least one performance characteristic selected from a simulated bottom hole cutting pattern, a simulated total imbalance force, a simulated side rake imbalance force, a historic Beta angle between radial and circumferential imbalance forces, and a historic trajectory of a simulated dynamic centerline. 
     
     
       8. The method of  claim 1 , wherein simulating further comprises:
 modeling of the drill bit dynamically drilling in the formation without constraining a centerline of the drill bit to be coaxial with a centerline of a bore hole. 
 
     
     
       9. The method of  claim 8 , wherein modeling of the drill bit dynamically drilling in the formation without constraining a centerline of the drill bit to be coaxial with a centerline of a bore hole, further comprises constraining the dynamic movement of the centerline of the drill bit based upon drill string parameters. 
     
     
       10. The method of  claim 1 , wherein simulating further comprises:
 modeling of the drill bit dynamically drilling in the formation while constraining the dynamic movement of the centerline of the drill bit based upon drill string parameters. 
 
     
     
       11. The method of  claim 1 , wherein the cutters in the cone region have faces at an original position and wherein adjusting the side rake angle of at least a cutter comprises moving the cutter so that the face of the cutter is moved forward in the direction of bit rotation of an imaginary radial plane, the imaginary radial plane passing through a centerline of the drill bit and through an original position of a center of the face of the cutter. 
     
     
       12. The method of  claim 1 , wherein:
 the simulating comprises calculating a wear pattern on a plurality of cutters on the fixed cutter drill bit over the simulated drilling time; and 
 the determining comprises entering the calculated wear pattern corresponding to the period of simulated drilling time. 
 
     
     
       13. The method of  claim 1 , further comprising displaying at least one performance parameter graphically, and wherein:
 the simulating comprises simulating the drilling in the earth formation for a period of simulated drilling time; 
 the determining comprises determining the at least one performance parameter for the period of simulated drilling time; and 
 the adjusting the side rake angle of at least one cutter comprises adjusting a side rake angle distribution of a plurality of cutters along the cone region of at least one blade of the fixed cutter drill bit to improve the at least one performance parameter according to the graphically displayed performance parameter. 
 
     
     
       14. The method of  claim 13 , further comprising repeating the simulating, determining, displaying, and adjusting the side rake angle distribution to optimize the performance parameter. 
     
     
       15. The method of  claim 13 , wherein adjusting the at least the side rake angle distribution of the cutters along the cone region of the blade of the fixed cutter drill bit comprises adjusting the cutters in the cone along a plurality of blades of the fixed cutter drill bit. 
     
     
       16. The method of  claim 15 , wherein the drill bit comprises a dual set drill bit having leading blades and trailing blades and wherein adjusting at least the side rake angle distribution of the cutters along the cone region of the blade of the fixed cutter drill bit comprises adjusting the side rake angles of cutters in the cone region along the leading blades to have an outward side rake angle and adjusting the side rake angles of the cutters in the cone region along the trailing blades to have an inward side rake. 
     
     
       17. The method of  claim 1 , wherein the adjusting produces a side rake angle distribution such that the at least one cutter has a side rake angle greater than 15 degrees and less than 90 degrees. 
     
     
       18. A method for designing a fixed cutter drill bit, comprising:
 simulating the fixed cutter drill bit drilling in an earth formation; 
 determining at least one performance characteristic for the fixed cutter drill bit; 
 adjusting at least the side rake angle distribution of cutters at least along a cone region of a blade of the fixed cutter drill bit to change the at least one performance characteristic of the fixed cutter drill bit. 
 
     
     
       19. The method of  claim 18 , further comprising repeating the simulating, determining, and adjusting at least the side rake angle distribution of the cutters to optimize the performance characteristic. 
     
     
       20. The method of  claim 18 , further comprising adjusting at least the side rake angle distribution of the cutters along a nose region of the drill bit. 
     
     
       21. The method of  claim 20 , wherein adjusting at least the side rake angle distribution of the cutters along the cone region and along the nose region of the blade of the fixed cutter drill bit comprises adjusting the side rake angle distribution such that cutters toward a center of the cone region have larger side rake angles than cutters toward the nose region of the drill bit. 
     
     
       22. The method of  claim 21 , wherein adjusting at least the side rake angle distribution of the cutters along the cone region of the blade of the fixed cutter drill bit comprises adjusting the side rake angle distribution such that cutters at a center of the cone region have relatively larger side rake angles than cutters along the nose region of the drill bit and such that the side rake angles progressively blend from the relatively larger to the relatively smaller side rake angles. 
     
     
       23. The method of  claim 18 , wherein the adjusting produces a side rake angle distribution such that a cutter in a cone region has a side rake angle greater than 15 degrees and less than 90 degrees and a cutter in a nose region has a side rake angle smaller than the side rake angle of the cutter in the cone region.